Process for producing tubular structures coated on both sides

ABSTRACT

Process for continuous production of inside and outside coated artificial tubular structures by first coating one side, thereafter applying vacuum from the other side to remove gases and impregnate the tube and then coating the second side and thereafter solidifing, washing and drying the tube, this process being carried out in a continuously working apparatus.

United States Patent Jager [451 May 9,1972

[54] PROCESS FOR PRODUCING TUBULAR STRUCTURES COATED ON BOTH SIDES 72] Inventor: Eugen Jager, Bomlitz, Germany [73] Assignee: Wolff & Co. Aktiengesellschaft, Walsrode,

Germany [22] Filed: June 4, 1969 [21] App1. No.: 830,405

[30] Foreign Application Priority Data June 8, 1968 Germany ..P 17 71 564.9

[52] US. Cl ..ll7/68, 117/94, 117/95, 117/119,117/166,118/50 [51 Int. Cl ..B05c 9/04, B44d 1/40 [58] Field of Search ..117/68, 94, 95,119,166; 93/94, 77 CL; 99/166, 169, 176; 118/50; 156/195 [56] References Cited UN1TED STATES PATENTS 8/1916 Subers ..118/50 7/1938 Huckfe1dt et a1. ..117/95 X 2,201,457 5/1940 Smith et a1. .1 17/68 UX 2,460,480 2/1949 Wolff ..1 17/95 X 2,584,660 2/1952 Bancroft ..99/166 UX 2,910,380 10/1959 Shiner ..117/95 X 3,376,810 4/1968 Carson et a1. ....93/80 X 3,378,379 4/1968 Shiner et a1. 1 17/95 X 3,451,827 6/1969 Bridgeford... ..99/176 3,476,078 11/1969 King ..1 18/50 X FOREIGN PATENTS OR APPLICATIONS 1,369,173 6/1964 France ..117/68 750,888 1/1967 Canada ..117/119 Primary E,\un|iner-Wi11iam D. Martin Assistant E,\uminerM. R. Lusignan A!t0rneyP1um1ey, Tyner & Sandt [5 7] ABSTRACT Process for continuous production of inside and outside coated artificial tubular structures by first coating one side, thereafter applying vacuum from the other side to remove gases and impregnate the tube and then coating the second side and thereafter solidifing, washing and drying the tube, this process being carried out in a continuously working apparatus.

3 Claims, 1 Drawing Figure Patented May 9, 1972 E EEEEEUQQE INVENTOR EUGEN JAGER BY /%M/ 7MWM ATTORNEYS PROCESS FOR PRODUCING TUBULAR STRUCTURES COATED ON BOTH SIDES PRIOR ART The production of a tubular structure coated on both sides in the form of a sausage skin is already known inter alia from French Pat. Specification No. 1,369,173. In this process, a long-fiber tubular structure formed from a flat sheet is coated with viscose, first on its inside and then on its outside. In this process, the first internal coating of the tubular structure also acts as an impregnation, as the viscose passes outwards through the tubular structure and forms a coherent film on its outer surface. Only then is the outside of the tubular structure coated with viscose in a separate operation. In this conventional coating process, numerous air pockets can be left behind in the supporting film. The resulting impregnation faults reduce the mechanical strength and also the transparency of the finished sausage skin. In addition, the process is complicated because the impregnating inner coating must form a coherent film over the outside of the long-fibered paper before the outer coating can be applied. Since the product is exposed to air between the first and second coatings, the inner coating of viscose that has penetrated outwards through the layer of long-fiber paper can undergo surface coagulation, resulting inter alia in a reduction in the bond strength of the subsequently applied outer viscose layer.

OBJECT OF THE INVENTION It is an object of this invention to provide a process and an apparatus for the continuous production of tubular structures coated on both sides which would obviate all the disadvantages referred to above.

THE INVENTION This object is accomplished by a process for the continuous production of inside and outside coated artificial tubular structures made from long-fiber or fabric tubing which comprises a. coating the long-fiber or fabric tubing formed from a flat sheet on one side with a solution ofa film-forming material b. removing gases from the tube and simultaneously impregnating the tube by evacuating the long-fiber or fabric tubing obtained in step (a) on the noncoated side 0. coating the tube thus obtained on the evacuation side with a layer of a dissolved film-former and d. solidifying, regenerating, washing and drying the tube obtained in step (c) by methods known per se.

In addition to the advantageous removal of gases, the vacuum treatment, as a process stage inserted between the first and second coating operations, also enables the long-fiber or fabric material to be completely impregnated with the filmformer. In addition, the vacuum treatment makes the process less dependent upon the viscosity of the dissolved film-former used both for the first coating and for the subsequent impregnation. In other words, in addition to low viscosity liquid film-former solutions, it is now also possible to use solutions of higher viscosity for impregnation. In addition, the vacuum treatment enables impregnation to be carried out at a faster rate, thus dispensing with the hitherto usual prolonged intervals between the first and second applications of the filmformer solution.

Accordingly, the coating process can be carried out in three process stages which follow one another rapidly and are combined into a group, in a single apparatus so that, providing this apparatus is suitably designed, it is also possible completely to avoid intermediate surface coagulation under the effect of air.

In one particularly advantageous embodiment of the invention, the first coating of the long-fiber and/or fabric tubing, is carried out as the inner coating, and subsequent evacuation of the internally coated support is effected from all round the outside, in such a way that the tubing is freed from gases to the outside and completely impregnated with the outwardly migrating component of the coating material by applying vacuum, after which the tubing is coated from outside with a layer of dissolved film-former and is then solidified and regenerated by methods known per se and optionally washed and dried.

In this embodiment the tubing is most advantageously guided in a downward direction.

When the tube is guided in this direction, it is of course also possible initially to coat the supporting tube with dissolved film-formers from the outside, subsequently to evacuate it from the inside and finally to coat the inside too. It is however also possible within the scope of the invention to apply the process according to the invention to tubing guided in an upward direction both in the order:

(a) inner coating, (b) evacuation from outside, and (c) external coating of the supporting tube, and also in the order:

(a) outer coating, (b) evacuation from inside, and (c) inner coating of the supporting material.

The coating process according to the invention is not restricted to any one particular film-former, providing it can be dissolved and then solidified again from the solution. Thus, the coating agent may be a known solution of cellulose in xanthogenate (viscose), which is preferred, or of cellulose in cuprammonium (copper cellulose), although a solution of hydroxyethyl cellulose or acetyl cellulose may also be used as the coating agent. In addition to the aforementioned regenerated cellulose and cellulose derivatives, it is also possible to use corresponding known soluble and precipitable synthetic polycondensates or polymers as the film-formers.

In this connection, the film-former may optionally contain the usual stabilizing or adhesion-promoting additives, providing such additives are required for finishing the skin produced in accordance with the invention, such as for example lacquering, coloring and/or printing.

The coating process according to the invention is illustrated by, but not limited to, the following Example.

EXAMPLE A tube formed in conventional manner from a flat sheet of long-fibered paper is introduced into a forming device comprising a forming tube and a forming ring in such a way that the tube moving downwards initially comes into contact with a forming tube made from chrome nickel steel and is coated internally with a conventional viscose. Immediately after it has been internally coated, the tube passes through a zone in which the material to be treated is first freed from gases under the effect of a 50 Torr vacuum and is completely impregnated with the viscose penetrating the tube from inside to outside. Immediately afterwards, another layer of viscose is applied on the outside of the tube in the same apparatus in the absence of air. After regeneration, rinsing with water and drying carried out in conventional manner, the finished sausage skin, coated in accordance with the invention, is highly transparent with a surface that is glossy on both sides, the smooth inner surface making the sausage easier to unpeel.

By appropriately adjusting the vacuum, and also by varying the amount of material introduced per unit of time, it is possible to obtain coatings in a variety of thicknesses on the inside and/or outside of the tubes. Products having surfaces from semi-matt to high-gloss can be obtained in this way.

One embodiment of an apparatus suitable for carrying out the present invention is shown in section in the accompanying Drawing.

Referring now to the Drawing, the forming device is indicated by l. 2 indicates an inner forming tool and 3 indicates an outer forming tool. 4 indicates a tube to be coated according to the invention, moving downwards through the forming device 1. 5 indicates a solution-removing means and 6 indicates a vacuum lead. 7 and 7a indicate inner solutiondelivering means, and 8 indicates an outer solution-delivering means.

In the forming device 1, a fiber or fabric tube 4 which is to be coated by the process according to the invention is passed outside the inner forming tool 2 and inside the outer forming tool 3. The inner forming tool 2 is provided with solutiondelivering means 7 and 7a for delivering the film-former solution used to coat the inside of the tube 4. The outer forming tool 3 is provided with solution-delivery means 8 for delivering the film-former solution to coat the outside of the tube 4. The outer forming tool 3 is also provided with solution-removing means (for removing excess film-former solution) and vacuum means 6, which are both situated between the inner solution-delivering means 1 and 7a, and the outer solutiondelivering means 8.

In one particularly advantageous embodiment of the invention, the forming tool 2 is in the form of a former tube and is arranged inside the long fiber or fabric tube 4 to be coated, whilst the forming tool 3, containing the vacuum lead 6 and the means for delivering and removing film-former solution 5,7,7a and 8, is in the form of a forming ring and is arranged outside the long-fiber or fabric tube 4 to be coated in such a way that the vacuum lead 6 which is situated in the forming ring 3 outside the tube 4 and which is provided with solutionremoving means 5 for removing the film-former solution is arranged beneath the solution-delivering means 7,7a in the forming tube 2 for delivering the film-former solution used to coat the inside of the tube, and above the means 8 in the former ring 3 for delivering the film-former solution used to coat the other side of the tube.

It is of course also possible within the scope of the invention spatially to modify the apparatus in such a way that, in cases where the tube is guided downwards, the process stages take place in the following sequence:

(1') outer coating, (ii) evacuation from inside, and (iii) inner coatings, and, where the tube is guided upwards, in the following sequence:

(i) inner coating, (ii) evacuation from outside and (iii) outer coating, and also in the following sequence:

(1') outer coating, (ii) evacuation from inside and (iii) inner coating.

In all the embodiments described above, the vacuum lead 6 and the means 5,7,7a, and 8 for delivering and removing the film-former solution are with advantage in the form of annular slot chambers, the vacuum unit 5 at least having at least one annular slot chamber.

it is also of advantage for the forming tube 2 and/or the fonning ring 3 to consist of a transparent chemically resistant plastics material.

The major advantage of the mode of operation of the apparatus according to the invention is embodied in its combined functions for forming, internally and externally coating, evacuating or removing gases and impregnating the long-fiber or fabric tubes to be treated. In addition to the already mentioned significant improvements, the effect of a vacuum upon the supporting tube has the further advantage that the supporting tube is drawn by the vacuum on to the inner wall of the forming tube and is thus additionally guided within the apparatus according to the invention. The effect of the vacuum on the guiding of the tube provides one means for adjusting the thickness of the layers of film-former on the inside and/or the outside of tubular structures. Any irregularities that may occur in layer thickness can thus be continuously eliminated by readjusting the vacuum during operation. In one embodiment of the former ring of transparent plastics material which also lies within the scope of the invention, coating and impregnation may be continuously controlled during operation to considerable advantage.

I claim:

1. A process for the continuous production of inside and outside coated artificial tubular structures made from longfiber or fabric tubing which comprises the steps of a. coating one side of a flat sheet formed into said tubing with a solution of a film-forming material,

b. simultaneously removing gases from the said tube and impregnating said tube with the solution of film-forming material by applying a vacuum to the non-coated side and area of said tubing, c. coating the tube thus obtained on the said non-coated side with a layer of a dissolved film-former and d. solidifying, and drying the coated tube obtained in step 2. The process of claim 1 wherein said coating step (a) is applied to the inside of long-fiber fabric tubing, and said evacuating and impregnating step (b) and said coating step (c) is applied from the outside of long-fiber fabric tubing.

3. The process of claim 1 wherein said steps (a) to (c) are carried out by guiding the long-fiber of fabric tubing in a.

downward direction. 

2. The process of claim 1 wherein said coating step (a) is applied to the inside of long-fiber fabric tubing, and said evacuating and impregnating step (b) and said coating step (c) is applied from the outside of long-fiber fabric tubing.
 3. The process of claim 1 wherein said steps (a) to (c) are carried out by guiding the long-fiber of fabric tubing in a downward direction. 